Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden and does much of it: it discloses the three side effects, that price is shown to the owner before purchase, that only standard registrations are handled, and the asynchronous pending_approval path with its follow-up. It stops short of permissions, reversibility/refund behavior, or timing expectations for registration.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the core action and its side effects, then the constraints and the async path in descending order of importance. No filler sentences; every clause carries operational meaning.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a paid, side-effecting tool with no output schema and no annotations, the description covers the critical return case (pending_approval) and the required agent behavior. It leaves cost visibility, failure/refund handling, and registration timing unaddressed, which keeps it just below fully complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so env/project/domain/years are already documented, including the '1-10, default 1' constraint and the domains.search prerequisite. The description adds only the abstract constraint 'standard registrations only', which is a marginal gain over the schema baseline.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource (buy a domain) and expands the scope with the concrete effects — registers it, points DNS at Plinth, issues HTTPS. Combined with the schema hint to run domains.search first, an agent can distinguish this from domains.connect/domains.verify without opening another schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives real routing conditions: 'Standard registrations only' excludes non-standard cases, and the pending_approval flow tells the agent exactly what to do (inform owner, then poll approval.status). It does not, however, contrast domains.buy against domains.connect or domains.orders, so the alternative-selection guidance is incomplete.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.